''DEVICE AND METHOD FOR PROTECTION OF A FIBER PATH NETWORK''

Abstract

The invention discloses a virtual protection method of a fiber path. The method physically divides an optical port into multiple minimum protection units. Based on the minimum protection units, a system is divided into more than one logic-systems. In a logic-system, each node can work in one of four working modes: normal working mode, passing working mode, bridging working mode and switching working mode. When protection is needed, a node is switched from normal working mode to other three working modes through multiplex section protection, or subnetwork connection protection, or channel protection etc. The invention also discloses a virtual protection device of a fiber path. The invention not only solves disadvantages of the present protection mode, but also makes transmission networking more flexible. This protection mode better satisfies user requirement. 13

Full Text

Field of the Technology
The present invention relates to a virtual protection method and device for a fiber path, and provides an extended protection method based on various present protection methods of a SDH (Synchronous Digital Hierarchy) fiber network, such as protocol protection, channel protection etc.
Background of the Invention
At present, people have more and more requirement to network bandwidth, and there are many advantages of SDH transmission, so size of a fiber network is developed rapidly and continuously. Consequently, self-healed protection of fiber network is getting important. According to ITU-T proposal, main protection methods of SDH fiber transmission network are channel protection, multiplex section protection and sub-network connection protection etc. Among them, the multiplex section protection is a most popular protection mode for present transmission network, including 1+1 liner multiplex section protection, 1:N liner multiplex section protection and 2/4 fiber uni-directional/bi-directional multiplex section shared protection
The basic principle of multiplex section protection is by transferring switching information through kl/k2 bytes in SDH frame to implement protocol switching function. Nevertheless, as kl/k2 bytes are located at multiplex section in SDH frame, one fiber line, or one optical port, can only transfer one set of kl/k2 bytes. This means one fiber can only belong to one multiplex section system, i.e. general multiplex section is based on optical port multiplex section. There is a disadvantage of this kind of protections: it cannot flexibly implement appreciate protection based on different services and causes waste of VC (virtual container) 4 resource on an optical port. The reason of so many SDH protection modes is that it is necessary to have different protection modes for different application situation. For example, for application that requires shorter switching time, for example switching time within 20 ms, multiplex section protection may not satisfy the requirement, so channel protection may be used.
In addition, multiplex section switching has an inherent disadvantage of its protocol byte, i. e there are only four bits to present node number, a ring at most can only support 16 nodes (excluding REG node, i.e.-regenerate node). When there are more than 16 nodes in a ring, only other protection modes can be used.
In addition, suppose network topology is as shown in figure 1, wherein nodes A, B, C and D compose the ring 101 and nodes A, B, C, D and E compose the ring 102. When ring 101 deploys multiplex section protection or channel protection, service between nodes B and E or between nodes D and E can not be protected. Similarly, when ring 102 deploys multiplex section protection or channel protection, services between nodes B and C or between nodes D and C can not be protected.
In practice, as SDH network is getting complicated, the phenomenon said above is very popular.
Summary of the Invention
The objective of the invention is to provide a protection method and device of fiber path to overcome the protection shortcoming said above. It not only provides fuller protection, but also makes networking flexibly and provides better protection mode to user.
To achieve the said objective, the present invention relates to a protection method for a fiber path in a fiber network, which comprises a plurality of nodes interconnected by optical fibers, each optical fiber and node being connected by a optical port, every two nodes communicating through a fiber path consisting of nodes and fibers, comprising of.
physically dividing the optical port into a plurality of minimum protection units,
dividing the fiber network into a plurality of logic-systems according to network topology, level and protection mode, dividing the minimum protection units to different logic-systems ; for every node in each logic-system , working in one of four working nodes: normal working mode, passing working mode, bridging working mode and switching working mode,
in case of a trouble in a fiber path, switching normal working mode to other working mode by each node in every logic-system to which the minimum protection unit of the fiber path port belongs
When multiplex section happens, the step (d) further comprises: d 1) creating logic-systems for protection switching;
d2) obtaining four sets of pages: working, switching, bridging and passing by analyzing current configuration;
d3) defining whether a node is a passing node, or a bridging node□or a switching node; and
d4) sending down a passing page under the passing node, sending down a bridging page under the bridging node and sending down a switching page under the switching node.
Wherein the step d) can further comprises:
d5) if the node sends down a passing page, then input protection bus of the node is directly passed to output protection bus of the node; if the node sends down a bridging page, then output working bus of the node is replaced with input protection bus of the node; if the node sends down a switching page, then output protection bus of the node is replaced with input working bus of the node.
In the scheme mentioned above, the said minimum protection unit is VC4 (virtual container 4) or VC3, which takes one or many VC4 or VC3 of multiple VC4 or VC3 to map to different logic-systems to form more than one logic-system.
In the method, when protection switching of a logic-system is happening, only services of a logic-system, which satisfy logic-system protection switching trigger condition, participate the protection switching.
The method further comprises:
uniquely adjusting and crossing services, which come from different minimum protection units and go to a same minimum protection unit, to the same protection unit by a time-division cross-connect unit.
The invention also proposes a virtual protection device of fiber path, which at least comprises:
a paging analyzer, analyzing configuration of a logic-system, creating corresponding working pages and storing the working pages in the switching controller said below;
a switching controller, sending down a corresponding working page to the cross-connection panel said below according to switching state;
a cross-connection panel, performing bus connection appropriately according to the sending down working page.
Wherein the working page is normal working page, or passing page, or bridging page, or switching page.
Wherein the cross-connection panel connect directly input working bus of a current node with output working bus of the current node, or input protection bus of a current node with output protection bus of the current node, or input protection bus of a current node with output working bus of the current node, or input working bus of a current node with output protection bus of the current node.
With the scheme above, as logic-systems are separated based on minimum protection unit, which can be VC4, VC3 etc., and an optical port can have multiple minimum protection units, so an optical port can be divided into multiple logic-systems. Consequently, different services can flexibly select different protection modes, and different logic-systems (different service, different network) can have different switching conditions. Therefore, transmission networking is more flexible and protection mode is better-satisfied user requirement. As same one system can be divided into multiple logic-systems, every logic-system can have different protection mode and breaks down the present technology situation: a system must be either this protection mode or that protection mode. In this way, more nodes can be included in the protection system; the node E in Fig.l, which cannot be protected by convention mode, can be protected. Obviously, the invention protection is more flexible, comprehensive and satisfactory.
Brief Description of the Drawings
Fig. 1 is a diagram shows that two rings cannot be protected simultaneously.
Fig.2 is a diagram shows that different service uses different protection mode. Fig. 3 is a diagram for bus-cross method of an embodiment of the invention.
Fig.4 is a diagram implementing unidirectional multiplex section switching of an embodiment of the invention.
Fig. 5 is a diagram for multiplex section switching algorithm of the invention.
Fig. 6 is a present networking diagram.
Fig.7 is a division diagram of logic-systems for virtual path protection.
Fig.8 is a structure diagram for virtual protection device of a fiber path of the invention.
Embodiments of the Invention
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
Fig. 2 shows that the invention can implement protection of multiple services such as Image service, voice service, signaling service and oversea service etc. Different services can deploy different protection modes. The core thinking of the technical scheme of the invention is shown below.
The first is minimum protection unit concept. This is based on that an optical port can be physically divided into one another VC4, and a minimum protection unit is a VC4. For example, a 622Mbit/s optical port can be seen as four independent VC4, because its transmission payload is four VC4.
The second is bus concept. A SDH transmission system can be roughly divided into branch units, line units and cross-connect units. The logic-system division of the invention is a division of line units and branch units. A switching page said below is generated by this division. Different divisions generate different switching pages, and switching execution is mainly performed by the cross-connect unit. For an add/drop multiplex equipment, there are many services can be added or dropped, for example, 2Mbit/s, 34Mbit/s and 155Mbit/s etc.; and capacity of a line can be 155Mbit/s, 622Mbit/s and 2.5Gbit/s etc. It is impossible to select different cross-connect units for different line capacities or different adding and dropping services. When a low priority service is added to a line, it will be multiplexed to a VC4; a time-division
cross-connect unit can be used for crossing, which uniquely adjusts and crosses services coming from different VC4 to the VC4 expected. Here, a VC4 can be considered as the basic speed rate of a bus unit. Fig.3 shows meaning of the bus crossing. In the left-hand side of the arrow of Fig.3, there are three different VC4s: VC4#1, VC4#2 and VC4#3; and there are shaded blocks represent second unit of first VC4 (1,2), third unit of second VC4 (2,3) and first unit of third VC4 (3,1), respectively. The right-hand side of the arrow shows that after bus time-division cross connecting, a SDH system multiplexes services coming from three different VC4s to one same VC4 which sequentially transfers services loaded on (3,1), (1,2) and (2,3).
The third is logic-system concept. As a node can belong to different basic network topology and each network may have different protection mode, a physical media with same basic topology, same level and same protection mode can be seen as a whole, called logic-system. Characteristics of a logic-system are as follow: level, such as 155M, 622M, 2500M etc.; network element type, such as add/drop multiplexer (ADM), terminal (TM) and regenerator (REG); service direction, such as uni-directional, bi-directional; protection mode, such as channel protection, multiplex section protection, 1+1 protection, 1:N protection, sub-network connection protection etc.; fiber number, such as 2 fibers, 4 fibers; and basic network topology type, such as ring, link, etc. ADM logic-system includes east direction line, west direction line and selectable branch. TM logic-system includes east direction/west direction line and selectable branch. With these characteristics, working page and protection page are generated by analyzing add/drop service or passing through service. Logic-system concept simplifies services configuration and provides possibility for implementing protection flexibly.
When protection switching of a logic-system is happening, if other logic-systems do not satisfy the trigger condition of the logic-system protection switching, then only services on the logic-system participate the protection switching procedure, i.e. there is logic independence.
The fourth is bus replacing concept. Multiplex section switching can be performed by the idea: one end node of a path changes to bridge mode, other end node changes to switching mode and middle node changes to passing through mode, as shown in Fig.4. Fig.4 is a diagram implementing unidirectional multiplex section switching of an embodiment. In Fig.4, left part of the arrow is the network topology, which includes two fibers ring, one working channel and one protection channel, and
four nodes A, B, C and D on the ring. In Fig.4, right part of the arrow shows working states of working channel and protection channel of three types of node: the passing node, the bridging node and the switching node; among them blank block represents working channel and shaded block represents protection channel. When fiber 401 between nodes B and C has trouble, working channel and protection channel between nodes B and C cannot work any more. The transmission services between nodes B and C or the transmission services passing through nodes B and C will transfer to the destination node through protection channels between BA, AD and DC. At this moment, node B will be bridged, node C will be switched and nodes A and D will be passed, i.e., node B is a bridging node, node C is a switching node and nodes A, D are passing nodes. In this embodiment, suppose 1-4 in every node are working channel input buses, l'~4' are working channel output buses, 5~8 are protection channel input buses and 5'~8' are protection channel output buses. It can be seen from Fig.4, for a passing node (such as nodes A and D), signals inputted to protection channel input buses (5, 6, 7, 8) are cross-connected to protection channel output buses (5', 6', 7', 8'); for a bridging node (such as node B), signals outputted originally from working channel output buses (1', 2', 3', 4') are transferred to protection channel output buses (5', 6', 7', 8'); for a switching node (such as node C), signals inputted originally to working channel input buses (1, 2, 3, 4) are changed to protection channel input buses (5, 6, 7, 8).
It is possible for every node to deal with all switching situations, so every node needs to prepare four pages: normal page, passing page, bridging page and switching page. The normal page comes from analyzing logic-systems, and other pages are based on normal page with bus replacement. In the invention, "replacement" and "switching" are two different concepts; replacement is a number meaning, for example, input bus 1 is replaced by input bus 9; but switching is about network element which is an action of logic-system, for example, we say logic-system has a multiplex section switching, but we cannot say logic-system has a multiplex section replacement; switching is a changing from working part to protection part.
According to the concepts mentioned above, the invention, a virtual protection method of fiber path, comprises the following steps:
a□ an optical port is physically divided into multiple minimum protection units;
b□ according to service requirement, the minimum protection units, which belongs to multiple protection channel, of each optical port are divided into different logic-systems, so there are more than one logic-systems and an optical port is divided into multiple different logic-systems;
c□ in each logic-system, each node can work in one of the four working modes: normal working mode, passing working mode, bridge working mode and switching working mode;
dD when protection is needed, normal working mode is switched to other three working modes through multiplex section switching.
The fifth is protection independence concept. Different protection characteristics have different protection conditions. Channel protection is based on channel tributary-unit alarm-indicator-signal (TU-AIS) etc. Multiple section protection is based on multiplex-section alarm-indicator-signal (MS-AIS) etc. Different protections logically belong to different network topologies and, in general, take different physical paths, so protection will not happen at the same time. Therefore, it is required that a logic-system protection does not affect other logic-systems working mode.
Fig. 5 shows a simple flowchart of implementing multiplex section switching algorithm. First, create a logic-system for multiplex section protection. Then, according the configuration, four working pages: normal working page, switching page, bridging page and passing page will have been analyzed. A normal working page is from input working bus to output working bus. A switching page is from output protection bus to input working bus. A bridging page is from output working bus to input protection bus. A passing page is from input protection bus to output protection bus. The node is a bridging node or a switching node or a protection node or a passing node is analyzed by a protection switching controller. If the node is a bridging node, then a bridging page is sent down and the output working bus is replaced by the input protection bus. If the node is a switching node, then a switching page is sent down and the output protection bus is replaced by the input working bus. If the node is a passing node, then a passing page is sent down, and the input protection bus is directly passed to the output protection bus. In Fig.4, when there is a fiber trouble between nodes B and C and multiplex section switching is needed, the system needs to tell what changes should be happened for nodes A ~ D, respectively,
by analyzing current normal working pages of every node and the trouble position. After analyzing, it is defined that nodes A and D are a passing node, node B is a bridging node and node C is a switching node; then nodes A and D send down a passing page, node B sends down a bridging page and node C sends down a switching page. It can be seen from the switching algorithm that bus switching is different from convention switching mode (there is all VC4s on a port taking part the switching) with that VC4s belong to the logic-system take part the switching. Therefore, number of VC4s taking part a switching can be configured according to requirement and other VC4s can be used for other protections.
Fig.6 is a diagram of a networking topology with present technology used in somewhere. Along counter-clockwise direction, network elements A, B, C, D, E, F and G compose the ring 601; network elements H, I, J, K, L, M, N and O compose the ring 602; and the two rings are connected by G, H and F, I. Services in the ring 601 and the ring 602 can be protected by means of multiplex section protection mode or other protection modes, but services between rings can not be protected.
Fig.7 shows fiber rings although which have same networking topology as Fig.6, but logic-system division of the invention is used; so any part of the fiber network can be protected. In Fig.7, along counter-clockwise direction, network elements A, B, C, D, E, F and G compose the virtual-ring 701, network elements H, I, J, K, L, M, N and O compose the virtual-ring 702, and network elements A, B, C, D, E, F, I, J, K, L, M, N, O, H and G compose the big virtual-ring 703.
In virtual-rings 701 and 702, multiplex section protection can be used to protect services in the rings; and channel protection can be used for ring 703 to protect services between rings. In this design, each node is configured to two logic-systems; according to service requirement, all VC4 of each fiber can be mapped to a multiplex section logic-system or part of each fiber VC4s can be mapped to a multiplex section logic-system. For logic-system which composes the virtual-ring 703, as the logic-system spans more nodes and channel protection occupies more resource, so in general, one or several VC4s of all optical port are mapped to the logic-system according to the number of services and the level of optical ports.
Fig.8 shows structure of virtual protection device which implements the virtual protection method, mentioned above, of the invention. The virtual protection device of fiber path at least includes three parts: Paging analyzer 801, Switching controller
802 and Cross-connection panel 803. Each node sends appropriate working page
according to itself current switching state, and performs appropriate bus connection.
The page analyzer 801 is used for analyzing configuration of a logic-system, creating four working pages: normal working page, passing page, bridging page and switching page, and storing them to the switching controller 802. As each node of all nodes has many logic-systems, so there are many sets of pages and every page is related to a logic-system. The switching controller 802 is used for sending down a working page to the cross-connection panel 803, according to switching state. The cross-connection panel 803 performs connection of corresponding buses. So switching action is performed.
All mentioned above are only better embodiments of the invention, which by no means to limit the protection scope of the invention.

protection-device for a fiber path in a fiber .network which a plurality of nodes interconnected by optical fibers,
each optical fiber and node being connected by a optical port, every two nodes communicating through a fiber path consisting of nodes and fibers wherein the device comprises:
a paging analyzer, analyzing configuration of a logic-system creating corresponding working pages and storing the working pages in the switching controller said below;
a switching controller, sending down a corresponding working page to the cross-connection panel said below according to the switching state; and
a cross connection panel, performing bus connection , appropriately according to sending down working page.
2. The device as claimed in claim!, wherein the or a working
pages
comprise a normal working page, a passing page, abridging page
.and switching page.
3. The device as claimed in claim 1, wherein the cross connection
panel connectsdirectly input working bus of a current node with
output working bus of the current node or input protection bus of
a current node with output protection bus of a current node or
input protection bus of a current node with output working bus of
a current node or input working bus of a current node with output
protection bus of a current node.
4. A protection method employing the device as claimed in claim
for a fiber path in a fiber network which comprises a optical port
and multiple nodes it is characterized that the method comprises
the steps of:
a. physically dividing the optical port into a plurality of
minimum protection units,
b. dividing the minimum protection units into different logic-
systems to form more than one logic systems;
c. for every node in each logic system, working in one of four
working node: normal working node, passing working
node, bridging working node and switching working node;
d. in case of a trouble in a fiber path, switching normal
working mode of each node to other three working modes.
5. The method as claimed in claim 4, wherein said switching in step
c is a multiplex section protection switching, or a sub-network
connection protection switching, or a channel protection
switching.
6. The method as claimed in claim 4, wherein for a logic-system
with the multiplex section protection mode, every node in the
logic-system generating four sets of pages: working, passing,
bridging and switching, which respectively corresponding to the
normal working mode, passing working mode, bridging working
mode and switching working mode.
if protection being necessary, said step c comprises:
cl) every node in the logic-system making a choice to confirm that it should be of a passing node, or a bridging node or a switching node and
c2) a passing node sending down a passing page under the passing node, a bridging node sending down a bridging page under the bridging node and a switching node sending down a switching page under the switching node.
7. The method as claimed in claim 4, comprises:
c3) if the node sends down a passing page, then minimum protection units which belong to the logic-system and which are in the port of fiber path as an input protection channel are directly passed to those in the port of fiber path as an output protection channel;
if the node sends down a bridging page, then minimum protection units which belong to the logic-system and which are in the port of fiber path as an output working channel are replaced with those in the fiber path as an input protection channel;
if the node sends down a switching page, then minimum protection units which belong to the logic-system and which are in the port of fiber path as an output protection channel are replaced with those in fiber path as an input working channel.
8. The method as claimed in claim 4, wherein the minimum
protection unit is a VC4 or a VC3; and mapping ope or more
VC4 among a plurality of VC4 of a same fiber port one or more
VC3 among a plurality of VC3 of a same fiber port into different
logic-system to form a plurality of logic-systems.
9. The method as claimed in claim 4, comprises:
uniquely adjusting and crossing services which come from different minimum protection units and go to-a same minimum protection unit, to the same protection unit,by a time-diresion
1ft A virtual protection method for a fiber path substantially as herein described with reference to the accompanying drawings.
It. A virtual protection device of a fiber path substantially as herein described with reference to the accompanying drawings.